1. Field of the Invention
The present invention relates to a receiver and a signal reproduction apparatus using it. More specifically, the invention relates to a receiver for receiving a transmission signal which includes data relating to a broadcast station, programs, etc. as well as a primary signal, and a signal reproduction apparatus using such a receiver.
2. Background of the Invention
Part of FM stations in Europe provide the RDS (radio data system) service, in which a primary audio signal is broadcast together with RDS data. The RDS data is a collection of digital data relating to a broadcasting station, programs, etc., and includes the following data:
PS data . . . Character data indicating a broadcasting station name
PI code . . . Program identification code
AF list . . . List of frequencies of the broadcasting stations that are transmitting the same program
PTY code . . . Identification code indicating the content of a program
PIN code . . . Program item number code
EON data . . . Information on other networks
The PI code is 16-bit data including a country code, a program code, etc., and is transmitted 11 times/sec. The AF list includes data of 25 stations at the maximum. The PTY code is a 5-bit code indicating a genre of a program such as news, pops, education, sports or information. The PIN code indicates a scheduled broadcast start time, and is used for a reserved reception.
The RDS data is subjected to encode processing for error correction, and a subcarrier signal having a frequency of 57 kHz (three times the frequency 19 kHz of the stereo pilot signal) is subjected to balanced modulation by the encode-processed RDS data. The modulated signal is added to and frequency-multiplied with a primary signal, i.e., a monaural signal or stereo composite signal, and the multiplied signal is transmitted as an FM wave.
Therefore, an FM radio capable of receiving the RDS data can be tuned to a particular broadcasting station or can receive a particular program.
In the following description, a broadcasting station practicing the RDS service is referred to as "RDS station," when necessary.
By the way, an audio apparatus called a component stereo set is constituted by combining an FM tuner, a cassette deck, a graphic equalizer (equalizer amplifier), a pre-main amplifier, etc. However, in terms of functions, a user merely selectively uses the respective devices constituting the audio apparatus.
As a result, in conventional audio apparatuses, even if a decoder circuit for the RDS data is provided in an FM tuner, a user cannot utilize the RDS service effectively. For example, although a broadcasting station name etc. are displayed by use of the RDS data while an RDS station is being received, a listener will not hear the start of a news program if a tape cassette is being reproduced. As another example, when an emergency broadcast is performed, a listener may not hear it.